Capping machines typically utilize multiple capping devices, also known as capping heads or headsets, for fitting pre-threaded caps onto containers to secure contents disposed inside the containers. A typical capping device includes a drive member operatively coupled to a drive source such as a drive motor or turret assembly. The drive source imparts rotation to the drive member. A capper body rotates with the drive member and slides relative to the drive member. A cap-engaging portion mounts to a bottom of the capper body via a torque dependent clutch such that when the capping device moves downwardly to engage a cap to thread onto a container, the clutch limits the amount of torque transmitted to the cap.
A spring acts between the capper body and the drive member to “soften” the impact of the capping device on the cap. In other words, the spring absorbs the impact of the downward motion of the capping device as the cap-engaging portion contacts the cap to thread the cap onto the container. Otherwise, the cap may not properly fit on the container. In some systems a biasing force provided by the spring, which slidably biases the capper body away from the drive member, is adjustable to adjust an axial force that ultimately acts on the caps. To ensure proper tuning of the biasing force, and provide consistent capping results, the capper body should slide freely relative to the drive member. Typically, the capper body includes a single shaft that slides within a bore in the drive member. Examples of such capping devices are shown in: U.S. Pat. No. 4,295,320 to Willingham; U.S. Pat. No. 4,254,603 to Obrist; and U.S. Pat. No. 6,240,678 to Spether. However, with this configuration, there is a chance that the shaft will bind up in the drive member and prevent uniform sliding movement. This could result in difficulty with processing lines and inconsistent capping results. To ensure that the capper body freely slides relative to the drive member, and to provide consistency in processing, there is a need in the art for an improved bearing mechanism disposed between the drive member and the capper body.